(a) Field of the invention
The present invention relates to a reactor for culturing microorganism used for treating sewage and wastewater, and more particularly to a bioreactor for sewage and wastewater treatment, in which the bioreactor is capable of agitating and supplying oxygen simultaneously.
(b) Description of the Related Art
Generally, methods of treating wastewater include a physical-chemical method and a biological method. The drawbacks of the physical-chemical method include high costs and the need to re-treat the products, while the biological method produces a relatively little amount of product after treatment by resolving a large amount of organism elements into carbon dioxide to be stabilized, or by removing organic matters contained in wastewater with the generation of methane gas.
In the biological treatment method, pollutants in wastewater can be resolved, detoxified, and separated by using mainly microorganisms. Hence, the method is applied to treat industrial sewage containing organic matter and sludge generated therefrom, and to secondarily treat life sewage. Due to the relatively low cost and the variations of work progress, the biological method has been most widely used all over the world.
Microorganisms that play a core role in biological treatment are mixed cultures including various microorganism populations such as bacteria, fungi, protozoa, and metazoa, which are cultured and multiplied in a bioreactor. Such microorganisms cleanse sewage and wastewater by resolving and removing organic pollutants, which nourish the microorganisms, while the microorganisms multiply using oxygen dissolved in wastewater.
The bioreactor is a device that provides conditions similar to those found in nature to allow facultative microorganisms to be efficiently cultured. The bioreactor supplies a culture solution, organic and inorganic media, and air to the inside of the bioreactor, and cultures and multiplies the microorganisms.
Since the bioreactor is directly related to the culture and multiplication of microorganisms, the efficiency of sewage and wastewater treatment or the activation state of microorganisms depends on the bioreactor.
As a prior art method to enhance the efficiency of sewage and wastewater treatment by employing a bioreactor, published PCT Application WO 96/15992 discloses a method of treating sewage by injecting four types of aerobic and anaerobic microorganisms into an aeration tank without exhausting unpleasant odors, noxious gases, and toxic substances.
However, the above-described method is not used to multiply microorganisms in the aeration tank, and instead is used for removing noxious gases, etc. by applying specific microorganisms obtained from nature to the sewage sludge. A drawback of the method is that it takes long time for the injected microorganisms to treat the sludge.
U.S. Pat. No. 5,376,275 discloses an activated sludge treatment process, wherein a sewage sludge component is fermented for a period of at least 15 days to form soluble carbonaceous substrates, the fermented sludge component is contacted with influent sewage to form a conditioned sewage, and the conditioned sewage is supplied to the activated sludge plant.
However, the above-described process is not used for multiplying microorganisms in the fermentation plant, and instead is used for the dephosporization and denitrification of the sludge by using microorganisms. This method also has the drawback that it takes long time, for example, from 15 days to 60 days, to treat the sludge.